Mathias Fröhlich said: > On Montag, 5. April 2004 14:10, Jim Wilson wrote: > > Mathias Fröhlich said: > > > On Montag, 5. April 2004 05:30, Jim Wilson wrote: > > > > > We should also pick a coordinate origin to report it relative to. If > > > > > JSBSim is using the (moving) c.g., then we're both bugged. :) > > > > > > > > Umm...I think it's all the same isn't it? It isn't like the ground is > > > > going to move under the FDM's altitude. Well maybe in the area around > > > > KSFO it could. But we could move that code to the FGEarthQuake class. > > > > :-) > > > > > > No it is not. Depending on the locations of the tanks and how much fuel > > > they will carry the agl will change in this case... > > > Andy is totaly right. > > > > I may be a little slow (monday morning here), but that does not tell me > > anything. We are talking about agl not the center of gravity. Is that the > > confusion? > Hmm, I don't think so. > But the center of gravity is not fixed within the aircraft. So if there is a > heavy fuel tank below the fuselage forexample, the center of gravity might be > a few inches lower than when the tank is dropped. Since the altitude/agl > currently used is the altitude/agl of the center of gravity the altitude/agl > changes with the aircrafts mass distribution. And this is not an effect of > the gear springs here. >
Oh...well that isn't particularly useful. I think Andy (YASim) is just applying the compressed gear position for whatever reason at a point below the origin. And JSBSim is doing as I said earlier. By origin I mean the fixed location on the airframe at which the FDM's currently report position. We are only doing one elevation query for the aircraft and it is being done at the location specified at the lon,lat being published by the FDM. This is a 3D intersection test. So just so folks don't get too worked up yet...there is only one ground elevation in the current code. In summary, I prefer what JSBSim is currently doing, and it doesn't seem we really need it to do more. Instrument modeling should be done in the instrumentation code. By virtue of the fact that the FDM reports both a location, attitude, and velocities you have everything necessary to model any sensor. Shifts in center of gravity can ONLY affect location and attitude so such effects are there already. It's hard to believe I know, but we really don't need anything more reported by the FDMs. Best, Jim _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
